Solid-state imaging devices with higher resolution are used in many commercial applications especially camera and also for other light imaging uses. Such imaging devices typically comprise of CCD (charge coupled device) photo detector arrays with associated switching elements, and address (scan) and read out (data) lines. This CCD technology is matured so much that now days millions of pixels and surrounding circuitry can be fabricated using the CMOS (complementary metal oxide semiconductor) technology. As today's CCD technology is based on silicon (Si)-technology, the detectable spectral ranges of CCD are limited to the wavelengths below 1 μm where Si exhibits absorption. Besides, CCD based imaging technique has also other shortcomings such as high efficiency response combined with high quantum efficiency over broad spectral ranges. This broad spectral detection is required in many applications. One of them is the free space laser communication where shorter (in visible ranges) and near infrared wavelengths is expected to be used. Image sensor array having broad spectral detection capability, disclosed in this invention, is expected to provide those features not available in today's CCD and other imaging (e.g. InGaAs, HgCdTe, or PbS) technologies. With well design of the array, appreciable resolution can also be achieved in image sensor array technology.
Detectors (a.k.a. photodiode or sensor pixel) especially of p/intrinsic/n (p-i-n) type conductivity have been studied extensively over the last decade for its application in optical communication. These photodiodes are for near infrared detection, especially the wavelength vicinity to 1310 and 1550 nm, where today's optical communication is dealt with. Present short-wave infrared (SWIR) p-i-n photodiodes usually suffers serious dark currents. Thus, minimizing the dark current would be desirable to improve the overall performance.